Investigation On Electromagnetic Transport Property Of Weyl Semimetal And Black Phosphorus

In this thesis,we theoretically investigate the electron transport through Weyl semimetal and black phosphorus.Our researches contain both fundamental physics of the transport properties of Weyl Fermions and their potential applications in electronic devices.Based on the primary principle,the transport properties of black phosphorus nano-devices are analog computation and analyzed.This thesis consists of five chapters as follows:Chapter 1 is the introduction about the background and research motivations of nano-materials and nano-devices.Especially attention has focus on Weyl semimetal and black phosphorus materials which have attracted a lot of researcher attention in recent years.We introduce the scattering matrix method and tight bound approximation model and Hatree-Fock and density functional theory.In Chapter 2,we first investigate electron tunneling through double magnetic barriers in Weyl semimetals,we theoretically investigate the transport in a magnetic/normal/magetic hybrid structure on the surface of a Weyl semimetal.We find a directional-dependent tunneling which is sensitive to the magnetic field configuration and the electric gate voltage.The momentum filtering behavior becomes more significant for two-delta-function-shaped magnetic barriers.There are many Fabry-Perot resonances in the transmission determined by the distance between the two magnetic barriers.The combined effects of the magnetic field and the electrostatic potential can enhance the difference in the transmission between the parallel and antiparallel magnetization configurations,and consequently lead to a giant magnetoresistance.In Chapter 3,we investigate electron tunneling through period magnetic barriers in Weyl semimetals.We investigate theoretically the transmission and conductance for square-shaped and delta-function-shaped parallel magnetic field configurations.We find that the transmission of electrons through the period barrier structures depends sensitively on the incident angles,the Fermi energy,the magnetic fields,and the electric gate voltages.The tunneling magnetoresistance in such systems can be tuned significantly by changing the magnetic field and the number of layers of the superlattice.We find that the electron transmission displays an interesting momentum-filtering feature,which can be controlled by tuning the incident angle,the Fermi energy,the magnetic field and the distance between the two barriers.The momentum filtering behavior becomes more obvious when increase the number of layers of the superlattice for square-shaped parallel magnetic field configurations.In the case of the delta-function-shaped period magnetic barriers,its momentum filtration property is independent of the superlattice layer number.This behavior offers us an efficient way to control the transport and pave a way to construct Weyl semimetal-based electronic devices.In Chapter 4,we investigate negative differential resistance in the edge-modified for zigzag black phosphorus nano-devices.First,we discuss the relative stability of ZPNR with different atomic edges.After optimizing the electronic structure,we studied the stability of the zigzag black phosphorus nano-band with edge saturation.Then,the effects of different edge saturated atoms on the black phosphorus nano-band were investigated.The self-consistently calculated current-voltage(I-V)characteristics for zigzag black phosphorus nano-devices with edge saturation.we find Such devices exhibit transport characteristics dependent on the marginal saturated atoms of N?H?O atoms,the characteristics of multimodal negative differential resistance are presented.In particular,we can get large negative differential resistance when the edge saturation of O atoms.This theoretical foundation for constructing new negative differential resistance devices in the future.In Chapter 5,we present a brief summary.